The present invention relates to methods and apparatus for inserting into the earth and extracting from the earth elongate members and, more particularly, to apparatus and methods for inserting wick drain material into the earth.
For certain construction projects, elongate members such as piles, anchor members, caissons, and mandrels for inserting wick drain material must be placed into and in some cases withdrawn from the earth. It is well-known that, in many cases, such rigid members may be driven into and withdrawn from the earth without prior excavation.
The present invention is particularly advantageous when employed to insert a mandrel carrying wick drain material into the earth, and that application will be described in detail herein. However, the present invention may have broader application to the insertion into and removal from the ground of other elongate members such as piles, anchor members, and caissons, especially when these members must be driven at an angle with respect to horizontal. Accordingly, the scope of the present invention should be determined by the scope of the claims appended hereto and not the following detailed description.
Because wick drain material is flexible, it cannot be directly driven into the earth. Instead, it is normally placed within a rigid mandrel that is driven into the earth. Once the mandrel and wick drain material have been driven into the earth, the mandrel alone is removed from the earth, leaving the wick drain material in place. The wick drain material that is left in place wicks moisture in its vicinity to the surface to stabilize the ground at that point.
Conventionally, two types of systems are employed to drive mandrels into and remove mandrels from the earth. A first system is referred to as a top drive system and engages the upper end of the mandrel to insert the mandrel into the earth. In a top drive system, the upper end of the mandrel is securely attached to the drive system and forced downward or upward to insert the mandrel into or remove the mandrel from the ground. The upper end of the mandrel may also be vibrated by a vibratory drive means and/or crowded by a chain or cable drive means to cause the mandrel to penetrate the earth.
The primary disadvantage with the top drive system is that they require a substantial boom structure to support the mandrel and associated drive means. The requirement of a large and heavy boom structure limits the length of the mandrel that may be driven by a top drive system. Further, as the ground into which the wick drain material is to be inserted may be wet and unstable, the ground may not be sufficiently stable to support the required boom structure. Top drive systems thus may be inappropriate in certain situations.
The conventional second system for inserting and removing mandrels engages the bottom end of the mandrel and will be referred to herein as a bottom drive system. A bottom drive system is not attached to any one point on the mandrel; instead, rotating roller surfaces and/or gear teeth engage the mandrel in a manner that displaces the mandrel along its axis to drive it into the ground.
Bottom drive systems require a boom sufficient to support only the mandrel; the boom for a bottom drive system may thus be significantly lighter than that for a top drive system, which alleviates some of the problems associated with large booms.
However, the primary disadvantage with known bottom drive systems is that they rely entirely on the roller or gear drive system for insertion and removal of the mandrel. Bottom drive system do not have the benefit of a vibratory device for situations in which the mandrel becomes stuck due to soil conditions. In addition to conventional top drive systems and bottom drive systems, the Applicant of the present invention has developed a variation on the bottom drive systems that integrates a bottom gear drive with a vibratory device. The Applicant""s device will be referred to herein as the vibratory bottom drive device and is described in U.S. Pat. No. 6,039,508.
In the vibratory bottom drive device, the mandrel extends through the vibratory device such that the vibratory loads are applied substantially along the longitudinal axis of the mandrel. The vibratory forces are applied to the mandrel through a gear drive system that allows the mandrel to be driven by the crowding forces generated by the gear device and/or the vibratory forces generated by the vibratory device.
In practice, the vibratory bottom drive device works well. However, the need generally exists for a more flexible vibratory bottom drive system having components arranged to minimize wear and increase reliability.
U.S. Pat. No. 5,213,449 to Morris shows, and USSR Patent No. SU 1027357 appears to show, bottom drive devices for driving a mandrel into the ground. The Morris patent discloses a gear dive system and the USSR patent appears to show a roller drive system.
Top drive wick drain inserters are disclosed in U.S. Pat. No. 3,891,186 to Thorsell, U.S. Pat. No. 4,166,508 to van den Berg, U.S. Pat. No. 4,755,080 to Cortlever et al., Dutch Pat. No. 65252, Dutch Pat. No. 7805153, and Dutch Pat. No. 7,707,303.
The Thorsell patent employs a chain attached to the top of a wick drain mandrel to crowd the mandrel into the ground.
The van den Berg patent employs a two-part mandrel, with the two parts being wound around rollers and crowded into the ground by unwinding the rollers.
The Cortlever et al. patent discloses a cable connected to the upper end of the mandrel and a hydraulic system for displacing the cable to drive or crowd the mandrel into the ground.
The Dutch ""252 and ""153 patents appear to employ a chain to drive or crowd a mandrel into the ground.
In the Dutch ""703 patent, a vibratory device appears to be fixed to the top end of the mandrel to drive the mandrel into the ground.
Shown in U.S. Pat. Nos. 5,117,544 and 5,117,925 issued to the Applicant are vibratory devices for driving piles into the earth. These patents disclose placing the vibratory device on top of the pile to be driven and vibrating the pile along its axis; the combination of the vibratory forces along the axis of the pile and the weight of the pile and vibratory device drives the pile into the ground. Caissons may be driven into the ground in the same manner.
The present invention is a system for inserting and removing elongate members. The system includes a drive rack, a support assembly, a vibratory assembly, a drive assembly, and a shock absorbing member. The drive rack is formed on at least one surface of the elongate member. The support assembly supports the elongate member at a desired location on the ground.
The vibratory assembly comprises a vibratory housing defining a vibratory chamber and a vibratory axis and a vibratory system mounted within the vibratory chamber to generate a vibratory force along the vibratory axis.
The drive assembly comprises a drive housing comprising a main portion defining a drive chamber and, in certain configurations, a sleeve portion defining a sleeve chamber, where a drive axis extends through the drive chamber and the sleeve chamber and a drive system mounted within the drive chamber and comprising a drive gear that rotates to generate a drive force along the drive axis.
The shock absorbing member mounts the vibratory housing onto the support assembly to reduce the transmission of vibratory forces from the vibratory housing to the support assembly. The drive housing is attached to the vibratory assembly such that the drive axis, the vibratory axis, and a longitudinal axis of the elongate member are substantially aligned and the sleeve portion extends through at least a substantial portion of the vibratory chamber. The elongate member extends through the drive chamber and the sleeve chamber such that the drive gear engages the drive rack to transfer at least one of the vibratory force and the drive force to the elongate member and thereby displace the elongate member relative to the ground.